The present invention relates to a combination of split bodies for use in forming a synthetic resin blower fan by a so-called hollow article molding process. More specifically, the present invention relates to a combination of split bodies for use in forming a blower fan by the hollow article molding process. The blower fan includes a circular base, a doughnut-shaped cap having an air inlet at the center thereof, and radial blast-air channels formed between.
Heretofore, an air blower has been used in various apparatuses such as operating machines including a power blower and a sprayer. The power blower includes a blower fan rotatably driven by any suitable drive unit such as a two-stroke internal combustion engine. Most of the conventional power blowers have a similar structure which includes a circular base, a doughnut-shaped cap having an air inlet at the center thereof, and a plurality of vanes radially extending therebetween. A radial blast-air channel is formed between a pair of the vanes adjacent to each other.
The cap of the conventional blower fan is typically screwed or riveted to bosses formed in a thickened wall portion of the vanes.
Generally, each configuration of the blast-air channel defined by the vanes determines a good part of the blowing performance of the blower fan. In a conventional structure, it is required to form the bosses in the vanes which causes to provide significant restrictions in design. In addition, an additional process is required, for example, to screw which results in undesirably increased labor and time in a manufacturing process.
As described in xe2x80x9cNikkei Mechanicalxe2x80x9d (May 2000, pp 122-127), Japanese Patent Publication No. Hei 2-038377, and Japanese Patent Laid-Open Publication No. Hei 11-138584, a hollow article molding process is known. The hollow article molding process disclosed in the above publications will be briefly described below.
Two split bodies to be united with each other are primarily molded with a molten synthetic resin by using a forming die. Then, without releasing the molded split bodies, the forming die is moved so as to couple the split bodies with each other. While the spilt bodies are kept at sufficiently high temperature, the coupled split bodies are secondarily molded by injecting and filling a molten synthetic resin in a space formed between respective coupled peripheral edges of the split bodies. Thus, by the melted peripheral edges because of the heat of the molten synthetic resin and, additionally, by the molten synthetic resin itself, the split bodies are fusedly bonded to each other. The term xe2x80x9chollow article molding processxe2x80x9d herein means the process as described above.
The hollow article molding process may be classified, for example, into two processes; a DSI (Die Slide Injection) process and a DRI (Die Rotating Injection) process, depending on a motional direction of a forming die used in the molding. In the DSI process, after forming two split bodies as preliminary molded products, the forming die is opened with the preliminary molded products left within cavities thereof. Then, the forming die for the preliminary molded products is slid in a linear motion to couple the two split bodies with each other. According to the above-mentioned secondary molding process, the coupled split bodies are fusedly bonded with each other. In the DRI process, the forming die is rotated with two split bodies left within cavities thereof to couple the two split bodies with each other. Then, the above-mentioned molten synthetic resin is injected in a space formed between the coupled surfaces of the split bodies to fusedly bond the split bodies to each other. Irrespective of these motional directions of the forming die, the term xe2x80x9chollow article molding processxe2x80x9d stated herein is intended to encompass any mode of the process defined as above.
It is an object of the present invention to provide a combination of split bodies which allow a blower fan to be assembled by a hollow article molding process.
In order to achieve the above object, the present invention provides a combination of split bodies for use in assembling a synthetic resin blower fan by a hollow article molding process. The split bodies comprises a first split body and a second split body assembled on top of the first split body, the first split body including a circular base portion and a plurality of vanes extending radially, the second split body being a doughnut-shaped cap with an air inlet at the center thereof, radial blast-air channels being formed between adjacent pair of the vanes, the second split body including a plurality of grooves which are formed on an inner surface opposite from the first split body in an assembled state and each of which extends radially along an edge of a corresponding vane, each of the groove being adapted to be closed by the edge so as to define a flow path for allowing a molten synthetic resin to pass therethrough, and the second split body further including an injection hole being in fluid communication with an upstream end of the flow path with respect to the flow direction of the molten synthetic resin to be injected so as to allow the molten synthetic resin to be injected into the flow path therethrough, and a gas vent hole being in fluid communication with the downstream end of the flow path with respect to the flow direction.
The split bodies according to the present invention are molded and bonded as follows. The first and second split bodies are primarily molded with a molten synthetic resin by using a forming die. Subsequently, the forming die is moved, leaving the first and second split bodies therewithin, so as to align each of the vanes of the first split body with the corresponding groove of the second split body in opposed relationship to each other and to bring them into contact with each other. This allows each of the grooves to be closed by the corresponding vane so as to define a flow path for a molten synthetic resin. In this state, the gas vent hole at the downstream end of the flow path is in fluid communication with another gas vent hole which is formed in the forming die and in communication with the atmosphere.
In this state, a molten synthetic resin is injected into the injection hole. This molten synthetic resin flows through the flow path toward the downstream thereof. The injected molten synthetic resin extrudes the air in the flow path through both the gas vent holes to the atmosphere. In the flow path, the molten synthetic resin makes contact with the inner wall surface of the groove and the wall surface of the edge of the vane, and thereby these wall surfaces are fused by the heat of the molten synthetic resin. Any gas generated by the melting synthetic resin forming both of the split bodies is also discharged through the gas vent holes to the atmosphere. When a sufficient quantity of the molten synthetic resin is injected to fill the flow path completely, the operation for injecting the molten synthetic resin is completed. Then, the molded blower fan is released from the forming die. Additionally, an operator may visually confirm whether the entire flow path has been filled with the molten synthetic resin by checking the presence of at least small quantity of the molten synthetic resin flowed out of the gas vent hole of the second split body.
The split bodies according to the present invention allow the blower fan to be integrally formed by an injection molding process, which provides a simplified manufacturing process. Further, each edge of the vanes is fusedly bonded with the second split body by the hollow article molding process. This eliminates the need for providing the boss formed in the vanes to mount the doughnut-shaped cap. Thus, the restrictions in designing the blast-air channels are significantly reduced, and a desirable blower fan structure can be designed freely in view of the above-mentioned performance of the blower fan.
Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description.